Map Datum; Course History - Humminbird NS25 Operation Manual

North Reference determines the course and bearing calculations, relative to true magnetic north.
To set North Reference:
1. Highlight North Reference.
2. Select True or Magnetic. The factory setting is True.

Map Datum

Map Datum selects the geodetic datum for drawing the map.
CAUTION: This setting must match the datum used to create the map. Typically, this setting does
not need to be adjusted.
To set Map Datum
1. Highlight Map Datum.
2. Select the datum for the map, the factory setting is WGS 84. If Custom is selected, then
select Set-Up. The custom Datum Set-Up menu displays.
3. Select the appropriate Ellipsoid, DX, DY, and DZ values.
Note: Make sure your settings for the custom datum match the map source.

Course History

Course History sets the time intervals used to plot the course history trail. This is represented by
a trail of squares.
To set Course History:
1. Highlight Course History.